Robots, such as articulated-arm robots, for example, which can be used in various industrial fields, have, dependent on the intended field of application, several links which can be moved by means of joints, which links may be arranged in different ways. An important component of these robots are torque sensors for detecting the torques of the movable links. In most cases, these torque sensors are installed in or on all movable links of the robot.
The prior art has provided various systems for the detection of torques. WO 2009/083111, for example, describes a system for torque detection which uses strain gauges. These strain gauges are connected in two Wheatstone bridges (Wheatstone measuring bridge or bridge circuit) for the purpose of evaluation. The resistors of two strain gauges are arranged on two different locations of a component connected to the movable link and are each connected to form a half bridge. These two half bridges each form a bridge circuit. Another bridge circuit is formed by the resistors of two additional strain gauges, which are arranged on two additional different locations of the component. Thanks to the redundant design of the strain gauges, two torque values are detected. In order to ensure the functionality, a comparing means compares the signals of the same torque emitted by the two bridge circuits and shuts down the robot if the two signals differ beyond a certain tolerance range.
The systems and methods for torque detection known in the prior art nevertheless have the disadvantage that a deformation of the strain gauge apart from the torque load, which can be caused, for example, by compression of the strain gauge due to transverse forces, axial forces and bending moments, can lead to different signals even though no error is present. Different signals result in a measuring inaccuracy and this variance can, if a certain limit value is exceeded, lead to an emergency shutdown of the robot without there being any cause for doing so.
The problem addressed by the present invention is therefore to provide a sensor and a corresponding method which allow the above-mentioned disadvantages to be avoided and with which more precise and less error-prone detection of torques is possible. Another problem addressed is to provide a robot which is improved accordingly.